1. Field of the Invention
This invention relates to an improvement in apparatus for producing line scan and transverse graphic records of analog data, such as the variations with time of electrical data signals.
2. Description of the Prior Art
Graphic display apparatus for producing so-called line scan and transverse records are known in the prior art.
In transverse recording, the curves or traces representative of the variations with time of the analog data signals are produced across the width of the record sheet rather than along the length thereof, as in line scan recording. That is to say, transverse records proceed with time tranversely of the direction in which the record sheet is being moved relatively to the cathode ray tube.
As those skilled in the art understand, there are optimum speeds at which the record sheet must be moved with respect to the cathode ray tube, in both line scan and transverse recording, for the production of curves or traces having desirable aspect ratios. This optimum speed is different for data signals having different rates of variation, and hence, the line scan and transverse recording apparatus of the prior art usually is provided with an adjustable speed driving servo motor mechanism for moving the record sheet.
In the operation of such prior art line scan and transverse recording apparatus, it is the practice, in order to avoid unnecessary consumption of record sheet, to energize the cathode ray tube and its related circuits for a brief period before the driving servo motor mechanism for moving the record sheet with respect to the cathode ray tube is in motion. This is desirable in order to provide a warm-up period for the cathode ray tube and its related electronic circuitry. Also, in this period, the operator is provided an opportunity to check and to observe the performance of the circuitry and to make any necessary adjustments. When the servo motor mechanism is subsequently activated, there is a period during which the driving servo is accelerating in which the speed of movement of the record sheet relative to the cathode ray tube is less than the selected optimum value for the curves or traces to be recorded. In this period, there is a pronounced tendency for overlapping and illegibility of the curves or traces that are produced. If, after the record sheet has reached the selected optimum speed, the latter should become significantly less than the optimum value, there again will be a tendency for such overlapping and illegibility of the curves or traces.